Gy Interface Support
▀ Features and Terminology
▄ Cisco ASR 5x00 Packet Data Network Gateway Administration Guide
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Capabilities Exchange Messages: Capabilities Exchange Messages are exchanged between the diameter peers to
know the capabilities of each other and identity of each other.
Capabilities Exchange Request (CER): This message is sent from the client to the server to know the
capabilities of the server.
Capabilities Exchange Answer (CEA): This message is sent from the server to the client in response to
the CER message.
Important:
Acct-Application-Id is not parsed and if sent will be ignored by the PCEF/GW. In
case the Result-Code is not DIAMETER_SUCCESS, the connection to the peer is closed.
Device Watchdog Request (DWR): After the CER/CEA messages are exchanged, if there is no more traffic
between peers for a while, to monitor the health of the connection, DWR message is sent from the client. The
Device Watchdog timer (Tw) is configurable in PCEF/GW and can vary from 6 through 30 seconds. A very
low value will result in duplication of messages. The default value is 30 seconds. On two consecutive expiries
of Tw without a DWA, the peer is taken to be down.
Important:
DWR is sent only after Tw expiry after the last message that came from the
server. Say if there is continuous exchange of messages between the peers, DWR might not be sent
if (Current Time - Last message received time from server) is less than Tw.
Device Watchdog Answer (DWA): This is the response to the DWR message from the server. This is used to
monitor the connection state.
Disconnect Peer Request (DPR): This message is sent to the peer to inform to shutdown the connection.
PCEF/GW only receives this message. There is no capability currently to send the message to the diameter
server.
Disconnect Peer Answer (DPA): This message is the response to the DPR request from the peer. On receiving
the DPR, the peer sends DPA and puts the connection state to “DO NOT WANT TO TALK TO YOU” state
and there is no way to get the connection back except for reconfiguring the peer again.
A timeout value for retrying the disconnected peer must be provided.
Tw Timer Expiry Behavior: The connection between the client and the server is taken care by the DIABASE
application. When two consecutive Tw timers are expired, the peer state is set to idle and the connection is
retried to be established. All the active sessions on the connection are then transferred to the secondary
connection if one is configured. All new session activations are also tried on the secondary connection.
There is a connection timeout interval, which is also equivalent to Tw timer, wherein after a CER has been sent
to the server, if there is no response received while trying to reestablish connection, the connection is closed
and the state set to idle.
Diameter Credit Control Application
The Diameter Credit Control Application (DCCA) is a part of the ECS subsystem. For every prepaid customer with
Diameter Credit Control enabled, whenever a session comes up, the Diameter server is contacted and quota for the
subscriber is fetched.
